Radiation therapy is a common curative procedure to treat cancer. The goal of the radiotherapy process is to expose the tumor to a sufficient dose of radiation so as to eradicate all cancer cells. The radiation dose is often close to the tolerance level of the normal body tissues. Therefore, it is necessary to determine the dosage levels in different parts of the irradiated body with high accuracy.
Intensity Modulated Radiation Therapy (IMRT) is a complex radiation delivery system, which typically utilizes static ports or dynamic delivery. There are many steps between the calibration of the beam of the therapy radiation unit to the determination of the radiation dose at the desired point of interest in the patient. The alignment of the radiotherapy simulators and treatment machines must be checked regularly to maintain accurate localization and treatment. A comprehensive quality assurance tool is needed in order to verify any series of tests, so that the absolute dose delivered is consistent with the planned dose. In radiation therapy, it is important to ensure that the absolute dose delivered is consistent with the planned dose, and that the critical spatial resolution of that dose is consistent with the planned dose distribution.
The verification of IMRT patient treatment dosages typically is accomplished with custom built or modified dose measurement phantoms. The phantom simulates the body tissue and utilizes dosimeters to measure the radiation dosage before the treatment process on the patient is commenced. Conventional phantoms have limited versatility and do not support multiple dosimetric tools.
Accordingly, a primary objective of the present invention is the provision of an improved phantom for dose verification for intensity modulated radiation therapy.
Another objective of the present invention is the provision of a phantom which supports the commissioning of the entire IMRT system, from imaging through treatment, and which supports verification of the individual treatment plan.
A further objective of the present invention is the provision of an IMRT phantom having versatility in utilizing various dosimeters, including ion chambers, MOSFETs, radiochromatic film, TLD chips, ready pack film, diodes and polymer gel.
Another objective of the present invention is the provision of an improved phantom which provides multiple locations throughout the entire phantom for placement of the dosimeters, so as to enable a clinician to evaluate high dose gradient areas, inhomogeheity regions, and dose distribution at sensitive structures.
Another objective of the present invention is the provision of a quality assurance phantom for radiation therapy having a static block and an adjustable dynamic block, with both blocks being adapted to receive dosimeters.
A further objective of the present invention is the provision of a phantom that selectively utilizes a plurality of film dividers.
A further objective of the present invention is the provision of a phantom having multiple functions, including absolute dose verification in multiple locations throughout the phantom, inhomogeneity correction verification of treatment planning systems, enhanced verification of dose distribution using multiple dosimeters, sensitive structure modules for critical dose distribution evaluation, an effective teaching aid for IMRT, patient plan verification, verification of spatial magnification within CT image, laser calibration tool in a CT suite, three dimensional volumetric verification of dose distribution using multiple dosimeters, comprehensive tool for quality assurance, and commissioning of IMRT treatment planning systems, depth dose verification, and module design for customization and upgrades.
These and other objectives will become apparent from the following description of the invention.
The phantom of the present invention includes a base with a pair of spaced apart parallel slots. A static block is fixed to the base, and a dynamic block is slidably mounted within the slots such that the space between the static and dynamic blocks is adjustable. One or more film dividers are sandwiched between the static and dynamic blocks. Ready-pack film is inserted adjacent each film divider. The static and dynamic blocks are each adapted to receive a plurality of dosimeters. The blocks and film dividers are oriented vertically upon the base. Clamps secure the static and dynamic blocks together. Preferably, the dosimeters are selected from the group consisting of ion chambers, MOSFETs, radiochromatic film, and TLDS. The selectivity of the film dividers and dosimeters produce a broad range of use in the treatment planning systems, including CT scanners, simulators and linear accelerators.